The instant invention relates to granular detergent compositions containing a particular mixture of anionic and nonionic surfactants, particular amounts of certain organic and/or inorganic salts and moisture. Such compositions are formulated to provide either low or high sudsing and effective detergent performance as well as product stability. Such compositions can be prepared using conventional detergent processing equipment.
Commercial synthetic detergent compositions have for years employed substantial amounts of inorganic phosphate salts as builder materials. Such phosphate builder materials serve to sequester or complex mineral ions commonly found in household tap water in order to prevent such ions from interfering with cleaning performance of the synthetic surfactant in such compositions. Phosphate builders also contribute to the physical stability of granular detergent products.
However, some recent studies have indicated that the phosphate class of builder materials may present an ecological problem because of the ability of these materials to act as a nutrient that promotes the growth of algae, thereby accelerating the biological aging (eutrophication) of natural water bodies. As a consequence of the possible harmful effects of the continued use of phosphate builder materials in substantial quantities, attempts have been made to materially reduce or eliminate the need for phosphate salts in commercial detergent compositions.
One method for compensating for the absence of mineral sequestering phosphate builder salts in detergent formulations has been to synthesize compositions containing surfactant systems which are particularly insensitive to mineral hardness in laundering solution. Such surfactant systems have, for example, included relatively mineral insensitive mixtures of anionic and nonionic surfactants. (See U.S. Pat. Nos. 2,543,744; 2,744,874; 2,875,153; 3,528,925; 3,563,091 and 3,619,119, and the copending U.S. patent application of Collins, Ser. No. 222,363 filed Jan. 31, 1972.) However, since most common nonionic surfactants used in these systems are liquid at room temperature, many formulations containing anionic-nonionic surfactant mixtures have been liquid in nature.
Attempts to achieve acceptable low- or no-phosphate, granular, mixed anionic-nonionic detergent compositions (and the resulting commercial advantages of granular products) by conventional spray-drying techniques have not been entirely successful. Addition of a nonionic surfactant to a spray-dried or "blown" anionic surfactant-containing granule creates problems from a performance (sudsing), a processing and a granule stability standpoint.
While the addition of nonionic surfactant to such granules does render the surfactant system less sensitive to dissolved water hardness (i.e. Ca.sup.++ and Mg.sup.++ ions) and, hence, more suitable for underbuilt or non-built detergent formulations, such nonionic surfactant addition has a tendency to reduce the foaming and sudsing performance generally desired as a marketing advantage for heavy-duty laundry products. Furthermore, inclusion of nonionic surfactants into spray-dried detergent granules aggravates difficulties in processing such granules, i.e. the nonionic surfactant, imparts physical properties to detergent composition slurries which render pumping, crutching and spray drying of such slurries extremely difficult. Finally, inclusion of nonionic surfactant into blown detergent granules (coupled with the elimination or material reduction of hygroscopic phosphate salt levels) generally renders the granular end product more susceptible to caking, pourability problems and stability problems upon storage.
Accordingly, it is an object of the present invention to provide low- and no-phosphate, mixed anionic/nonionic surfactant-containing spray-dried detergent compositions which are effective for washing and laundering in mineral-containing water.
It is a further object of the present invention to provide low- and no-phosphate, mixed anionic/nonionic surfactant-containing spray-dried detergent compositions which can have sudsing levels comparable to those of conventional fully-built, high-sudsing, anionic-surfactant containing compositions.
It is a further object of the present invention to provide low- and no-phosphate, mixed anionic/nonionic surfactant-containing detergent compositions in granular form having commercially acceptable caking properties, pourability and storage stability.
It is a further object of the present invention to provide low- and no-phosphate, mixed anionic/nonionic surfactant-containing, spray-dried detergent compositions which can be processed with conventional spray-drying equipment and apparatus.
It has been surprisingly discovered that by combining a particular mixed anionic/nonionic surfactant system with particular organic and/or inorganic salts and moisture in particular essential concentrations, detergent compositions can be formulated which accomplish the above objectives and which are superior in performance, physical characteristics and processability to similar compositions presently known in the art.